Method for treating bacterial effluents containing at least a Gordonia terrae CIP I-2194 ether

ABSTRACT

A process for the treatment of aqueous effluents containing at least one of the following ethers is described: ethyl tert-butyl ether (ETBE) and/or methyl tert-butyl ether (MTBE) and/or tert-amyl methyl ether (TAME) in order to reduce the concentration of these ethers. A bacterium  Gordonia terrae  CIP I-2194 is innoculated under aerobic conditions. In particular, a bacterium  Burkholderia cepacia  CIP I-2052 or a bacterium  Alcaligenes  sp. CIP I-2561 or a bacterium  Mycobacterium  sp. CIP I-2562 is added in the presence of a growth substrate and, optionally, of a cobalt salt, and the ether contained in the effluents is degraded by the bacteria thus innoculated until its mineralization. The process is useable in the ether-contaminated water treatment industry.

The invention relates to a bacterial treatment process by microorganismscapable of degrading at least one ether, in particular ethyl tert-butylether (ETBE) and/or methyl tert-butyl ether (MTBE) and/or tert-amylmethyl ether (TAME) contained in aqueous effluents.

It particularly relates to the water treatment industry.

It is known that methyl tert-butyl ether, designated hereafter by theterm MTBE, as well as tert-amyl methyl ether, designated hereafter bythe term TAME, are ethers which can be used in particular as oxygenatedadditives in unleaded gasolines with the aim of increasing their octanerating. The increasing use of additives such as MTBE, TAME or ethyltert-butyl ether, designated hereafter by the term ETBE, involves thestorage and transport of large volumes, mixed in gasolines inparticular. It is therefore necessary to know the behaviour of thesecompounds in case of accidental spillage leading to pollution of thesoil and underground or surface waters. MTBE is an ether produced by thecondensation of methanol with isobutene, TAME is an ether produced bythe condensation of methanol with isopentene and ETBE is an etherproduced by the condensation of methanol with isobutene. The structureof these compounds which comprise an ether bond as well as a tertiarycarbon, is such as to make them very resistant to biodegradation bymicroorganisms present in the environment.

The literature concerning the biodegradation of these different ethersused as additives in gasolines shows that the metabolism of thesecompounds requires in the majority of cases the use of bacteria or mixedcultures selected beforehand as their presence in the environment is notcommon (J. P. Salanitro et al., Demonstration of the enhanced MTBEbioremediation (EMB) in situ process, In Situ and On-SiteBioremediation, 19–22 Apr. 1999, San Diego, Calif.).

The Applicant has previously isolated a bacterium Gordonia terrae(ex-Gordona terrae) CIP I-1889 which has proved capable of growing,partially using ETBE as carbon and energy source, the ETBE beingdegraded to the stage of tert-butyl alcohol (TBA) which can then be usedas a carbon and energy source by another bacterium Burkholderia cepacia(ex-Pseudomonas cepacia) CIP I-2052 also isolated by the Applicant(Patent Application FR 2 766 478) or by a bacterium Alcaligenes sp. CIPI-2561 or a bacterium Mycobacterium sp. CIP I-2562 also isolated by theApplicant. It has been found that the bacterium G. terrae CIP I-1889,which is not capable of degrading MTBE or TAME using them as a carbonand energy source, is capable of degrading these compounds byco-metabolism when it is cultured in the presence of a suitable growthsubstrate such as for example ETBE or ethanol (Patent Application FR 2787 783). If the bacterium G. terrae CIP I-1889 is cultured on ethanoland in the presence of MTBE and/or TAME in mixed culture with thebacterium B. cepacia CIP I-2052, the MTBE and TAME are degraded to TBAand tert-amyl alcohol (TAA) respectively which can then be used as acarbon and energy source by B. cepacia CIP I-2052 (Patent Application FR2 787 783) or by the bacterium Alcaligenes sp. CIP I-2561 or thebacterium Mycobacterium sp. CIP I-2562.

However, the bacterium G. terrae CIP I-1889 has the drawback of having alatency phase in its growth.

One of the objects of the invention is to remedy the drawbacks of theprior art.

Another object is to describe an aerobic process which uses these newbacterium for the treatment of contaminated waters with the purpose ofdegrading the MTBE, ETBE or TAME contained in solutions and moregenerally in compounds containing at least one alkoxy group and inparticular a tert-alkoxy group. In so doing, the residual concentrationsof ether in urban or industrial waste water or aquifers contaminated bythese products or by fuels which may contain these oxygenated productsare significantly lowered.

In a more detailed manner, the invention relates to a process for thetreatment of aqueous effluents containing at least one ether, preferablyethyl tert-butyl ether (ETBE) and/or methyl tert-butyl ether (MTBE)and/or tert-amyl methyl ether (TAME) in order to reduce theconcentration of said ether, characterized in that at least onebacterium Gordonia terrae CIP I-2194 is grown under aerobic conditionsin the presence of a growth substrate and the ether contained in theeffluents is degraded in the presence of said substrate by the biomassof said bacteria thus produced.

According to an embodiment of the process, when the aqueous effluentsessentially contain MTBE, the MTBE contained in the effluents canadvantageously be degraded by also introducing into it, in a joint ordissociated fashion, at least one bacterium chosen from the group formedby Burkholderia cepacia CIP I-2052, Alcaligenes sp. CIP I-2561,Mycobacterium sp. CIP I-2562, Arthrobacter globiformis ATCC 53596,Bacillus coagulans ATCC 53595, Pseudomonas stutzeri ATCC 53602 andMycobacterium vaccae JOB5 ATCC 29678.

When used in this way, the tert-butyl ether is degraded to tert-butylalcohol (TBA) and the almost total degradation of TBA to carbon dioxideand water is carried out by the additional of the mentioned bacteriawhich have the capability to grow on the TBA thus produced. TheseStrains, B. Cepacia CIP I-2052, Alcaligenes sp. CIP-I-2561 andMycobacterium sp. CIP I-2562 have been deposited by the Applicant at theInstitut Pasteur (CNCM, 25, rue du Docteur-Roux, F-75724, PARIS, CEDEX).G. terrae CIP I-2194 has been deposited with the Institut Pasteur,Collection Nationale de cultures de Microorganism 25, Rue de DocteurRoux, F-75724, Paris, Cedex 15, on May 5, 1999 under accession numberI-2194. Any other bacterium capable of growing on TBA can also beincluded in the scope of the present invention.

According to another embodiment of the process, when the effluentscontain essentially TAME, the TAME contained in the effluents can bedegraded by also introducing into it, in a joint or dissociated fashion,a bacterium B. cepacia CIP I-2052 or a bacterium Alcaligenes sp. CIPI-2561 or a bacterium Mycobacterium sp. CIP I-2562 which have theability to also grow on tert-amyl alcohol (TAA) a degradation product ofTAME and to almost totally degrade it to carbon dioxide and water. Anyother bacterium capable of growing on TAA can also be included in thescope of the present invention.

According to another embodiment allowing an improvement in the growth ofthe bacterium B. cepacia CIP I-2052 or the bacterium Alcaligenes sp. CIPI-2561 or the bacterium Mycobacterium sp. CIP I-2562, it can be grown inthe presence of TBA and/or TAA and at least one cobalt salt, preferablycobalt chloride. Under these conditions, the concentration of TBA and/orTAA can be comprised between 0.01 and 10 g/L of effluents and that ofthe cobalt salt between 0.01 and 4 mg/L.

According to an embodiment of the invention, the bacterium G. terrae CIPI-2194 selected from G. terrae CIP I-1889 is generally innoculated on agrowth substrate which can be, for example, at least one compound chosenfrom the group formed by ethanol, isopropanol, n-butanol, n-pentanol, amonosaccharide, a disaccharide, dibutyl ether, ethyl butyl ether, ethyltert-butyl ether, acetone, ethylene glycol, glycerol and tryptone.

Other growth substrates based on carbon and hydrogen can be provided.

Each bacterium may grow differently in the presence of a given type ofsubstrate. Excellent results were obtained using ethanol and/or acetoneas growth substrates.

This particular growth substrate can be introduced at a concentrationwhich does not exceed the toxicity threshold of this substrate for thebacterium considered, for example at a concentration at least equal tothat of the ether to be degraded and advantageously comprised between0.1 mg/L and 5500 mg/L of effluents. Thus, it was noted that when thebacterium according to the invention is cultured in the presence of agrowth substrate which is ETBE, i.e. an aqueous effluent containing itand which one wishes to treat, it present no latency phase duringgrowth, contrary to what was observed when using G. terrae CIP I-1889.

When it is a question of degrading the MTBE and/or TAME contained in theaqueous effluents to be cleaned up, it was noted that the bacteriumaccording to the invention proved capable of initiating the degradationof these ethers, even in the absence of growth substrate. However, it ispreferable to use a growth substrate as described above and, forexample, ethanol or isopropanol.

This bacterium G. terrae CIP I-2194 is said to be constitutive for thedegradation of ethers, i.e. the enzymes responsible for the initialattack on the ethers are produced in a constitutive fashion and do notrequire a prior induction in order to be used. Such a strain which growsin the presence of a growth substrate such as ethanol willadvantageously be combined, within the scope of a mixed culture, todegrade the ethers ETBE, MTBE and/or TAME with the bacterium B. cepaciaCIP I-2052 or with the bacterium Alcaligenes sp. CIP I-2561 or thebacterium Mycobacterium sp. CIP I-2562 which are grown in the presenceof a cobalt salt. Under these conditions, the degradation of the etherstarts immediately and the resulting TBA and/or TAA is, in turn,degraded almost totally and very rapidly. The bacteria can tolerate awide range of ether concentrations. Preferably, aqueous effluents can bedegraded which contain a concentration of ether and, in particular, ofMTBE or TAME or ETBE at least equal to 5,000 mg/L and more particularlycomprised between 0.01 mg/L and 400 mg/L. Nevertheless it is stillpossible to dilute the effluent in order to operate under optimalconditions, compatible with the degradation capacities of the bacterialstrains.

In the case where the aqueous effluents contain ethyl tert-butyl ether(ETBE) as pollutant, this ETBE can be used at least in part as growthsubstrate and therefore as a source of energy.

The process ensuing from the use of these bacteria is applicable fortreating in particular effluents contaminated by MTBE, TAME and/or ETBE,so that the concentrations of MTBE or TAME or ETBE in discharges arecompatible with the regulations in force.

The growth substrate can be provided continuously or discontinuously ata concentration which ensures the supply of energy required forbiodegradation, for example at a concentration at least equal to that ofthe ether to be degraded.

The use of these bacteria for the treatment of effluents contaminated byMTBE or ETBE or TAME can be carried out in the following manner: forexample in a biofilter where the bacteria are fixed on a mineral ororganic support or they can be added as inoculum to sewerage plantsludges.

These bacteria can also be used for the in situ treatment ofcontaminated aquifers by injecting them as inoculum with a suitablegrowth substrate into shafts drilled in the aquifer.

When said bacteria are developed on a biofilter system of appropriatevolume, the effluents containing the ether, in particular MTBE, ETBEand/or TAME, can be introduced into the biofilter in the presence of airor oxygen at a suitable feed rate of 0.05 L/L to 5 L/L, for example of0.1 to 2 L/L biofilter/hour depending on the concentration ofcontaminant to be treated and the effluent rid at least in part of thecontaminating ether is drawn off.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the following examples andfigures of which:

FIG. 1 shows the MTBE degradation capacity of a culture of Gordoniaterrae CIP I-2194 in the presence of ethanol,

FIG. 2 illustrates the TAME degradation capacity of a culture ofGordonia terrae CIP I-2194 in the presence of ethanol,

FIG. 3 shows the residual concentration (RC) of substrate which isethanol and of MTBE as a function of time, and

FIG. 4 represents the optical density (OD_(600 nm)) expressing thegrowth of microorganisms as a function of time for a mixed culture of G.terrae CP I-2194 and B. cepacia CIP I-2052.

EXAMPLE 1 (COMPARATIVE)

Isolation of a New Strain of Gordonia terrae CP-2194 and Comparison ofits Growth with the Growth of Gordonia terrae CIP I-1889 in the Presenceof ETBE.

The bacterium Gordonia terrae CIP I-1889 is capable of growing on ETBE(Patent FR 2 766 478) which it uses as a source of carbon and energyresulting in the accumulation of tert-butanol (TBA). This bacterium wascultured by successive subcultures several times on the minimum mediumMM1 containing ETBE as source of carbon and energy and the compositionof which is as follows:

KH₂PO₄ 6.8 g K₂HPO₄ 8.7 g Na₂HPO₄, 2H₂O 0.33 g NH₄Ci 1.5 g CaCl₂, 2H₂O0.0364 g FeCl₃, 6H₂O 0.0012 g Solution of vitamins 1 ml H₂O q.s.f. 1liter pH-6.95

The solution of vitamins has the following composition per 1 liter ofdistilled water:

Biotin 200 mg Riboflavin 50 mg Nicotinamic acid 50 mg Panthotenate 50 mgp-aminobenzoic acid 50 mg Folic acid 20 mg Thiamine 15 mg Cyanocobalamin1.5 mg

ETBE is added to this medium at a high concentration, i.e. between 300and 500 mg/L.

At the end of these different subcultures, a new bacterium whichoriginated from the bacterium Gordonia terrae CIP I-1889 was obtained.It presents morphological and conventional characteristics identical tothose of the mother strain. It was deposited at the collection of theInstitut Pasteur, Paris, France as Gordonia terrae CIP I-2194. This newstrain is constitutive for the expression of genes which allow thedegradation of ETBE, i.e. the degradation of the ETBE occurs without theneed for prior contact of the strain with the ETBE. The mother bacteriumG. terrae CIP I-1889 is said to be inducible for the degradation of ETBE(ETBE⁺i) and the new strain G. terrae CIP I-2194 is said to beconstitutive for the degradation of ETBE (ETBE⁺c).

By way of comparison, the bacterium G. terrae CIP I-1889 on the one handand the bacterium G. terrae CIP I-2194 on the other hand are culturedseparately in a vial of the MM1 medium described above and to which ETBEis added as carbon and energy source (growth substrate) at a finalconcentration of the order of 1 g/L.

The cultures are incubated at 30° C.

The residual concentrations of ETBE are determined from samples takenfrom each of the cultures and injected into a gas chromatograph equippedwith an integrator which calculates the residual concentrations of ETBEand TBA produced by integration of the different peaks obtained in thechromatograms. The results obtained are presented in Table No. 1.

TABLE No. 1 Comparison of growth in the presence of ETBE of the bacteriaG. terrae CIP I-1189 and CIP I-2194 Latency phase observed Initial ETBEFinal TBA before Biomass Duration Strain concentration concentrationdegradation of produced of test % ETBE tested (mg/L) (mg/L) ETBE (hours)(mg/L) (hours) degraded G. terrae 985 714 94.5 206 190 100% CIP I-1889G. terrae 873 633 0 250 78 100% CIP I-2194

As can be seen from this experiment, no latency phase (delay) isobserved with the strain G. terrae CIP I-2194 for the degradation ofETBE. This is considered as an advantage for the use of the strains by aperson skilled in the art.

EXAMPLE 2

Degradation of MTBE and TAME by Gordonia terrae CIP I-2194.

The capacity of the bacterium G. terrae CIP I-2194 to degrade MTBE andTAME was studied.

The bacterium G. terrae CIP I-2194 is innoculated in flasks of the MM1mineral medium described in Example 1 and containing either MTBE or TAMEas carbon source at a concentration of the order of 200 mg/L.

The cultures are incubated at 30° C.

Samples are taken at regular intervals from these cultures in order todetermine by gas chromatography the residual contents of MTBE and TAME.

The results are shown in FIGS. 1 and 2.

As can be seen in these figures, from innoculation. the bacterium G.terrae CIP I-2194 is capable of degrading the MTBE and the TAME. Thisdrop in concentration of each of the ethers is correlated to theconcomitant appearance of the corresponding alcohol, i.e. TBA in thecase of the MTBE and tert-amyl alcohol (TAA) in the case of the TAME.Nevertheless, it is seen that although this degradation occurs without alatency phase, it is not total and stops after 40 to 60 hours ofincubation.

If ethanol is then added to the culture (after about 150 hours in thefigures), the degradation of the MTBE or TAME by G. terrae CIP I-2194then resumes and is total in about thirty hours.

This experiment indeed confirms that the behaviour of the bacterium G.terrae CIP I-2194 is different from that of the mother bacterium G.terrae CIP I-1889, as the latter was not capable of initiating thedegradation of the MTBE or the TAME in the absence of a growth substrate(Example 2 of Patent No. 98/16520). As the bacterium G. terrae CIPI-2194 is constitutive for the enzymes responsible for the attack on theether bond, it is capable of initiating the degradation of the MTBE orthe TAME although these compounds do not constitute a carbon and energysource, nevertheless this degradation is only partial as limitationsmust soon occur in the bacteria. The addition of ethanol which is thegrowth substrate then allows the degradation of the MTBE or the TAME tobe terminated by co-metabolism, as was described for the bacterium G.terrae CIP I-1889.

This ability to initiate the degradation of the MTBE or the TAME in theabsence of growth substrate constitutes an advantage of the bacterium G.terrae CIP I-2194 compared with the mother bacterium G. terrae CIPI-1889.

EXAMPLE 3 Degradation of MTBE by a Mixed Culture of Gordonia terrae CIPI-2194 and Burkholderia cepacia CIP I-2052 in the Presence of CobaltChloride

The degradation of MTBE by a mixed culture containing G. terrae CIPI-2194 and B. cepacia CIP I-2052 in a fermenter was studied. Apreculture of G. terrae CIP I-2194 was carried out on 200 mL of Luriamedium. A preculture of B. cepacia CIP I-2052 was carried out on 200 mLof MM2 medium the composition of which is as follows:

KH₂PO₄ 1.4 g K₂HPO₄ 1.7 g NaNO₃ 1.5 g MgSO₄, 7H₂O 0.5 g CaCl₂, 2H₂O 0.04g FeCl₃, 6H₂O 0.012 g Solution of vitamins 1 mL H₂O q.s.f. 1 liter

The solution of vitamins has the following composition per 1 liter ofdistilled water:

Biotin 200 mg Riboflavin 50 mg Nicotinamic acid 50 mg Panthotenate 50 mgp-aminobenzoic acid 50 mg Folic acid 20 mg Thiamine 15 mg Cyanocobalamin1.5 mgand containing glucose at a concentration of 500 mg/L and to which wasadded at a rate of 10 m/L of MM2 medium a solution of trace elementscontaining a cobalt salt which allows an improvement in bacteriumgrowth. This solution of trace elements has the following composition:

Nitrilotriacetic acid 1.5 g Fe(NH₄)₂(SO₄)₂, 6H₂O 0.2 g Na₂SeO₃ 0.2 gCoCl₂, 6H₂O 0.1 g MnSO₄, 2H₂O 0.1 g Na₂MoO₄, 2H₂O 0.1 g ZnSO₄, 7H₂O 0.1g AlCl₃, 6H₂O 0.04 g NiCl₂, 6H₂O 0.025 g H₃BO₃ 0.01 g CuSO₄, 5H₂O 0.01 gq.s.f. 1 liter of distilled water.

These precultures are used to innoculate 4 L of MM2 medium describedabove and to which the solution of trace elements containing the cobaltsalt described above was added at the rate of 10 mL/L of culture medium.Under these conditions, the two strains are at cellular concentrationsafter innoculation of the order of 10⁸ u.f.c./mL for G. terrae CIPI-2194 and 10⁷ u.f.c./mL for B. cepacia CIP I-2052. The fermenter is fedin batch mode, i.e. without drawing off. The feed contains a mixture ofthe substrate, ethanol at 100, g/L as carbon and energy source and ofco-substrate to be degraded, MTBE at 50 g/L. The feed rate is fixed at 1mL/h. The temperature of the fermenter was fixed at 30° C. The stirringwas 900 revs/min with aeration of 12.5L/Uh.

Samples were taken from the culture medium and the residualconcentrations of ethanol, MTBE and TBA are determined after filtrationby GC measurement. At the same time, counts are taken at regularintervals of each of the two strains G. terrae CIP I-2194 and B. cepaciaCIP I-2052, by plating on dishes of Luria medium and on dishes ofgelosed MM2 medium containing TBA at the rate of 500 mg/L. The resultsof these experiments are presented in FIGS. 3 and 4. The ethanolprovided is rapidly used by the bacterium G. terrae CIP I-2194 and atthe same time, the MTBE is also degraded to TBA without the appearanceof a latency phase during the simultaneous use of the substrate, ethanoland co-substrate. The TBA thus formed accumulates at a concentration notexceeding 30 mg/L, then is rapidly reconsumed by the bacterium B.cepacia CIP I-2052. From 40 hours, the residual concentrations ofethanol, MTBE and TBA are zero. The respective populations of the twostrains increase up to 80 hours of culture then stabilize due to thelimitation of substrate (ethanol or TBA). During this experiment whichlasted 210 hours, 2.4 g of injected MTBE has been degraded as well as5.2 g of ethanol. The quantity of TBA formed from the MTBE is 2 g, these2 g were also totally degraded.

EXAMPLE 4 Degradation of MTBE by Two Types of Mixed Cultures: 1)Gordonia terrae CIP I-2194 and Alcaligenes sp. CIP I-2561 or 2))Gordonia terrae CIP I-2194 and Mycobacterium sp. CIP I-2562 in thePresence of Ethanol or Isopropanol

3 different precultures are carried out:

-   -   a preculture of G. terrae CIP I-2194 on the MM2 medium described        in Example 3 and containing ETBE at 500 mg/L as carbon source.    -   a preculture of Alcaligenes sp. CIP I-2561 on the MM2 medium        containing TBA at 1 g/L as carbon source.    -   a preculture of Mycobacterium sp. CIP I-2562 on the MM2 medium        containing TBA at 1 g/L as carbon source.

After 48 hours' growth at 30° C. under agitation, these differentprecultures are centrifuged in order to recover the bacterial pellet ofeach strain. Each pellet is washed with MM2 medium then collected bycentrifugation.

The pellet of G. terrae CIP I-2194 is taken up in 4.5 mL of MM2 medium,the pellet of Alcaligenes sp. CIP I-2561 as well as the pellet ofMycobacterium sp. CIP I-2562 are each taken up in 20 mL.

The optical densities at 600 nm (O.D._(600 nm)) of these suspensionswere able to be measured for G. terrae CIP I-2194 and Mycobacterium sp.CIP I-2562 and they are 7.32 and 2.72 respectively. The O.D._(600 nm)was not able to be measured for Alcaligenes sp. CIP I-2561 as thisstrain forms flocculates.

These cellular suspensions were used to innoculate flasks of MM2 medium(50 mL) containing either isopropanol (300 mg/L final) and MTBE (100mg/L final), or ethanol (300 mg/L final) and MTBE (100 mg/L final). Thesuspensions are used at the rate of 1 mL for the strain G. terrae CIPI-2194 and 0.5 mL for one or other of the suspensions for Alcaligenessp. CIP I-2561 and Mycobacterium sp. CIP I-2562.

Non-innoculated control tests constituted by flasks of MM2 mediumcontaining isopropanol and MTBE or ethanol and MTBE are carried outunder the same conditions. The flasks are incubated under agitation at30° C. for 72 hours.

The initial O.D._(600 nm) was able to be calculated in the case of mixedcultures of G. terrae CIP I-2194 and Mycobacterium sp. CIP I-2562, it isapproximately 0.17. After 72 hours, samples of each culture and of thecontrols are taken, filtered (0.22 μm) and measured by GC in order todetermine the residual substrates. The results are shown in Table No. 2.

TABLE 2 Residual MTBE and ethanol or isopropanol contents of mixedcultures of G. terrae CIP I-2194 with Alcaligenes sp. CIP I-2561 orMycobacterium sp. CIP I-2562 Final Final Final Mixed culture MTBE FinalTBA ethanol isopropanol Final used content content content content0.D._(600 nm) G. terrae CIP 0 0 0 — n.d.* I-2194/ Alcaligenes sp. CIPI-2561 (ethanol + MTBE) G. terrae CIP 0 0 — 0 n.d.* I-2194/ Alcaligenessp. CIP I-2561 (isopropanol + MTBE) G. terrae CIP 0 0 0 — 0.41 I-2194/Mycobacterium sp. CIP I-2562 (ethanol + MTBE) G. terrae CIP 0 3.3 mg/L —0 0.44 I-2194/ Mycobacterium sp. CIP I-2562 (isopropanol + MTBE) *n.d:not determined

It was verified that in the controls neither the MTBE nor the ethanolnor the isopropanol in the mixture are degraded.

As can be seen from the results of this experiment, the MTBE is totallydegraded in the presence of isopropanol or ethanol by G. terrae CIPI-2194. The TBA formed during this degradation is then used byAlcaligenes sp. CIP I-2561 or by Mycobacterium sp. CIP I-2562 as acarbon and energy source. The ethanol or isopropanol are entirely usedup.

A second addition of MTBE and substrate, ethanol or isopropanol, in thesame quantity as during the first addition was carried out and theflasks were again incubated. The measurements were carried out after 24hours, then after 48 hours' incubation.

After incubation for 24 hours, there was no longer any MTBE, ethanol orisopropanol in any of the flasks. Also there was no longer any residualTBA in the flasks of mixed cultures of G. terrae CIP I-2194/Alcaligenessp. CIP I-2561. On the other hand, residual TBA remained in the mixedcultures of G. terrae CIP I-2194/Mycobacterium sp. CIP I-2562 but afterincubation for 48 hours there was no longer any residual TBA in thesemixed cultures.

The complete degradation of a second addition of MTBE/ethanol orMTBE/isopropanol indeed confirms the degradation capacity of thedifferent mixed cultures which were tested.

1. A process for the treatment of an aqueous effluent containing atleast one contaminant selected from the group consisting of ethyltert-butyl ether (ETBE), methyl tert-butyl ether (MTBE), and tert-amylmethyl ether (TAME) in order to reduce the concentration of saidcontaminant, wherein said process comprises growing at least onebacterium Gordonia terrae CIP I-2194 under aerobic conditions in thepresence of a growth substrate, wherein said contaminant contained inthe effluent is degraded in the presence of at least said growthsubstrate by at least the biomass of said bacteria thus produced.
 2. Aprocess according to claim 1, wherein the aqueous effluents essentiallycontain MTBE and further comprising introducing into said aqueouseffluent, in a joint or dissociated fashion, at least one furtherbacterium chosen from the group consisting of Burkholderia cepacia CIPI-2052, Alcaligenes sp. CIP I-2561, Mycobacterium sp. CIP I-2561,Arthrobacter globiformis ATCC 53596, Bacillus coagulans ATCC 53595,Pseudomonas stutzeri ATCC 53602 and Mycobacterium vaccae JOB5 ATCC29678, so as to degrade the MTBE.
 3. A process according to claim 2,wherein the bacterium Burkholderia cepacia CIP I-2052 or Alcaligenes sp.CIP I-2561 or Mycobacterium sp. CIP I-2562 is grown, in the presence oftert-butyl and/or tert-amyl alcohol and at least one cobalt salt.
 4. Aprocess according to claim 3, wherein the concentration of tert-butyland/or tert-amyl alcohol is comprised between 0.01 and 10 g/L ofeffluents and that of the cobalt salt is between 0.01 and 4 mg/L.
 5. Aprocess according to claim 3 wherein said at least one cobalt saltcomprises cobalt chloride.
 6. A process according to claim 5 wherein theconcentration of said cobalt salt is between 0.01 and 4 mg/L.
 7. Aprocess according to claim 1, wherein the aqueous effluents essentiallycontain TAME and further comprising introducing into said aqueouseffluent, in a joint or dissociated fashion, at least one furtherbacterium selected from the group consisting of Burkholderia cepacia CIPI-2052, Alcaligenes sp. CIP I-2561 and Mycobacterium sp. CIP I-2562, soas to degrade the TAME.
 8. A process according to claim 1, furthercomprising selecting the bacterium Gordonia terrae CIP I-2194 from abacterium G. terrae CIP I-1889 after successive subculturing of said CIPI-1889 in the presence of ETBE.
 9. A process according to claim 1,wherein the growth substrate comprises at least one compound chosen fromthe group consisting of ethanol, isopropanol, n-butanol, n-pentanol, amonosaccharide, a disaccharide, dibutyl ether, ethyl butyl ether, ethyltert-butyl ether, acetone, ethylene glycol, diethylene glycol, glyceroland tryptone, at a concentration at least equal to that of the ether tobe degraded.
 10. A process according to claim 1, wherein the MTBE, ETBEand TAME concentration of the effluent is at most equal to 5 g/L.
 11. Aprocess according to claim 10 wherein said concentration is between 0.01mg/L and 400 mg/L.
 12. A process according to claim 1, wherein saidbacteria are developed on a biofilter, the effluent containing at leastone of said contaminants is introduced into the biofilter in thepresence of air or oxygen at a feed rate of 0.1 to 2 L/L biofilter/hourand the effluent depleted at least in part of MTBE and/or TAME is drawnoff.
 13. A process according to claim 1, wherein the aqueous effluentcomprises an aquifer and into which said bacteria are injected asinoculum with the growth substrate, in the presence of air or oxygen,via shafts drilled in said aquifer.
 14. A process of according to claim1, wherein ether degradation enzymes are constitutively produced in saidCIP I-2194.
 15. A process for the treatment of an aqueous effluentcontaining at least one contaminant selected from the group consistingof ethyl tert-butyl ether (ETBE), methyl tert-butyl ether (MTBE), andtert-amyl methyl ether (TAME) in order to reduce the concentration ofsaid contaminant, wherein said process comprises growing at least onebacterium Gordonia terrae CIP I-2194 under aerobic conditions in thepresence of a growth substrate, wherein said bacterium shows no latencyin growth when cultured in the presence of the growth substrate, andwherein said contaminant contained in the effluent is degraded in thepresence of at least said growth substrate by at least the biomass ofsaid bacteria thus produced.
 16. A process for the treatment of anaqueous effluent containing at least one contaminant selected from thegroup consisting of ethyl tert-butyl ether (ETBE), methyl tert-butylether (MTBE), and tert-amyl methyl ether (TAME) in order to reduce theconcentration of said contaminant, wherein said process comprisesgrowing at least one bacterium Gordonia terrae CIP I-2194 under aerobicconditions in the presence of a growth substrate, wherein said bacteriumconstitutively produces the enzymes for reducing the concentration ofsaid contaminant, and wherein said contaminant contained in the effluentis degraded in the presence of at least said growth substrate by atleast the biomass of said bacteria thus produced.